Overdelivering in the shape of attending an overserved market hurts you.
You provide nice-to-haves.
Moving one extra pixel that only you notice.
Writing one more line of beautiful code, that only you care for.
Here’s the thing
If they’re nice-to-haves odds are, they’ll be mostly ornaments without a relevant job.
It’ll increase your workload while adding either more complexity to your customer or adding nice features they don’t actually care about.
You don’t need to prove anything.
All you need to do is one simple thing: keep your promise.